High voltage electric circuit breaker



Dec. 22, 1942. w. K. RANKIN 2,306,186

HIGH VLTAGE ELECTRIC CIRCUIT BREAKER Filed Jan. 27, 1941 2 Sheets-Sheetl Inventor Wliam K.Rankin,

g His Attorney.

De@ 22, 1942. w. K. RANK\N 2,306,186

HIGH vVOLTAGE ELECTRIC CIRCUIT BREAKER Filed Jan. 27, 1941 2Sheets-Sheet 2 Jygmpyalm inventor- \/\/i| lam K. Ranmn,

l-is Attorney.

-cipal object thev provision yblast circuit breaker operable at hightransmis- Patented D. .22, i942 William General Electric New York K'.Rankin, Lansdowne, Pa.,

assignor to Company, a corporation of Application January 27, 1941,Serial No. 376,21 8 Claims. (Cl. 20u-148) My invention relates to highvoltage lelectricl circuit breakers, more particularly to circuitbreakers or the gas blast type having separable contacts between which ablast of gas is directed for extinguishing arcing', and has for itsprinof an improved gas sion line voltages and capable of eicientlyinterrupting and clearing high voltage power circuits.

The interruption of a high voltage power circuit, such as for example a138 kv'. circuit, by means of a gas blast involves a number of difficultproblems due to the limited dielectric strength of gases (such as air)most commonly used. Heretoore, oil circ 't breakers have beenalmostexclusively used for ,such interrupting duty -since the dielectricstrength of oil is many times that of air. Accordingly, when the arc isextinguished at a current zero by the oil circuit breaker, theintervening oil dielectric is much better able to withstand thereturning recovery voltage than air. Reestablishment of the arctherefore does not occur and the circuit remains open. Air on the otherhand may be so stressed by the recovery voltage across the interruptinggap that breakdown occurs'. The power arc is thereby reignited andfailure of the breaker results.

In accordance with my invention, the high voltage range of a gasor airblast circuit breaker is greatly increased by utilizing the increaseddielectric strength o gas under pressure, during interruption, so as tominimize the danger of restriklng ofthe arc within the interruptingcharnber, without however impairing the arcex tinguishing action of theblast.

It is known that the dielectric strength of agas increases according topressure increase; also that, in a nozzle, a backpressure in excess of50% with no appreciable decrease in the velocity of the gas through thenozzle. My invention in combination makes effective use of thesephenomena by separating interrupting contacts to draw an arc in achamber in which a relatively high pressure exists, or is appliedco-incident with contact separation. This arc chamber pres- 'sure doesnot impede the velocity or impair the effectiveness of the interruptinggas blast. An

interrupter constructed in accordance with my invention is found to havethe same ability to interrupt current as one using a similar but freelyvented nozzle, and in addition is operable at much higher voltages.

of the applied pressure may -be permitted ing structure y cated at 1.

In practicing my invention, the interrupting chamber communicating withthe source of blast pressure is provided with a venting or exhaustopening having a suitable cross-sectional area that is related to theinterrupting chamber and blast pressure so as to insure effective blastvelocity for arc interruption while maintaining the interrupting chamberatmosphere surrounding the interrupting gap at a substantiallypredetermined related pressure. In order to provide for unusual orvariable operating conditions, means are also provided for furtherincreasing the aforesaid cross-sectional area of the exhaust blastopening in accordance with the pressure in 'the interrupting chamber.

My invention will be more fully set forth in the following descriptionreferring to the accompanying drawings, and the features of noveltywhich characterize my invention will be pointed out with particularityin the claims annexe to and forming a part of this specification.

Referring to the drawings, Fig. 1 is an elevational, sectional view of ahigh voltage gas blast circuit breaker ,embodying the present inventionin the closed circuit position thereof, Fig. 2 is an elevational View ofa single phase double-break outdoor circuit vbreaker of the charactershown by Fig. 1 with disconnecting means intermediate the dualinterrupting units, and Fig. 3 is a plan viewof Fig. 2 illustrating theoperation oi the disconnecting means.

Referring to Fig. 1, the high voltage circuit breaker comprisesessentially separable contacts I and 2 whichvare connected respectivelyto the breaker terminals 3 and 4. The rod contact I is relatively fixedand is held in position by conduct- 5 and a guide bushing 6 suitablyconnected to the 'conducting structure as indi- The contact I is mountedwithin and centrally oi the conducting structure 5 for limited movement,or wipe, as indicated at 8. In the position shown, the contact I is heldin contact engagement by means of a biasing spring 9 mounted within theconducting structure 5. Sliding contact structure I0 electricallyconnects the rod Contact I to the structure 5, which is in turnelectrically connected by the conductor Il to the breaker terminal 3.

The coacting or movable rod contact 2 is connected to an operatingpiston I2 operable within a cylinder I3 for moving the contact 2 intoand out of circuit making engagement with the contact I. The contact 2is electrically connected to the other breaker terminal at 4 through aconducting spring guide and bearing plate I4 carinterconnecting/ange 31"rled by the contact extension i2 (hereinafter.

described), a iiexible conductor I5 and a ilxed conducting spider I6.

-The contacts I and 2 are separable within an interrupting chamber I1which, in the present instance, is elongated and formed by an insulatingtube I 8 composed of mechanically strong insulating material; such ashard fibre. The insulating tube I8, which is capable of withstand-l inghigh internal vbursting pressures, is provided with an insulating liningI9 of suitable arc resisting insulating material. The insulating liningI3 forms at 20 substantially at the point of separation of the contactsI and 2 a restricted nozzlelike section in the interrupting chamber.lAccordingly, when gas under pressure is admitted to the lower end ofthe interrupting chamber, the arc gap formed at the constriction whenthe gas pressure has elevated the piston I2 causes an arc extinguishingblast longitudinally of. the arc as it is drawn into the upper part ofthe yinterrupting chamber I1.

The mechanical stresses incident tothe application of the gas blast(which may be introduced at approximately 350 lbs. per sq. in.) requirethat the interrupting chamber and its insulating structure as well aselectrically eiiicient at high voltages. To this end, the insulatingtube I8-is secured.` at its lower end, as by a ring-shaped clampingWedge 2| and clamping flange 22, to a base plate 23 (as indicated at23') that 24 to the lower terminal structure 3. The base plate 23 is anintegral part of the depending contact supporting structure 5 throughwhich a plural'ity of parallel connected gas passages 25 interconnectthe lower end of the arc .chamber and fthe gas supply conduit 26. Theupper` end of the insulating tube I8 is similarly secured to a topsupporting plate 21 .by a clamping ring 28 is in turn bolted at` in thecase of air be physically rugged and flange 29 that is bolted at 30 tothe top plate.

Between a pair of supporting anges 3I and 32 secured respectively to thetop plate 21 and the lower terminal base plate 3 is mounted a highvoltage insulator shell 33 surrounding and spaced with respect to thetubel I8. The insulating shell 33 is of the high Voltage outdoor typecomposed of ceramic material, such as porcelain, and is resilientlyconnected to the upper plate through a flexible corrugated coupling 34as illustrated for preventing transmission .of excessive shock to theporcelain insulator. The annular space 35 between the tube I8 and theinsulator 33 is preferably lled with a non-iniiammable insulating liquidof high dielectric strength, such as for example a liquid chlorinatedhydrocarbon described and claimed in Clark Patent No. 1,931,- 455,granted October 17, 1933, for YDielectric materials for electricaldevices.

The top plate 21 forms a base for supporting the piston cylinder I3 andits associated apparatus, the blast exhaust controlling means and thehousing 36 therefor. More specifically, the piston cylinder I3 issecured in position through by means of its integral concentricsupporting cylinder 431 which seats in an annular recess in the upperface of the supporting plate 21 and is clamped therein by nuts 39threaded on three evenly spaced studs 38 screwed into the supportingplate 21. Large ports 31' are provided in the supporting cylinder sidewall. The cylinder I3 is therefore rigidly secured to the supportingplate 21 and the lower end thereof, which is provided with ports 40directly communicating with the interrupting l chamber I1, is arrangedto admit gas under pressure tothe lower is spring biased toward closedcircuitl position.

The pistonv biasing means comprises in the present instance the movablespring bearing plate I4 on the end of the piston rod (and contact)extension I2"between which and the upper xed spring bearing plate (orspider) .I6 are mounted biasing springs 4I. The springs 4I are guided onthe through bolts 38 which are secured at their upper ends at 42 to thexed plate I6. The plate I6 in turn serves as an anchorage for the upperpart of the housing 36 which constitutes a dome-shaped cover member 36'.For the purpose of providing low gradient spring action, thespringbearing plates I4 are-provided with socketlike extensions I 4', inwhich the springs 4I are seated and which are guided for reciprocalvertical movement by .the through bolts 38. Accordingly, when the pistonI2 is raised by the blast pressure, the spring bearing plate I4 iscorrespondingly raised to compress the springs 4I, thereby storingenergy for closing the contact 2 upon cut-olf of blast pressure.

- For the purpose of controlling the operation of the contact piston I2so that there is no appreciable tendency to rebound near the end of theopening stroke, and also so that the breaker cam, ifl desired, bereclosed at the proper speed, the cylinder I3 is provided with valvemeans for controlling pressure within the cylinder. A by-pass connection43 between the interrupting chamber I1 and the upper part ofthe cylindertends to equalize pressure on both sides of the piston near the end ofthe opening stroke for slowing up the speed thereof. This eliminatesshockA and excessive stresses at the end of the opening stroke. ThisI`buffer action can be nicely. regulated and adjusted by a valve 43connected in the by-pass connection and by an adjustable bleed valveindicated 'at 44 connecting with the upper cyiinder space.

I In case excessive back pressure tends to build up in the uppercylinder space causing rebound of thepiston I2 with possiblereestablishment of arcing between the contacts, a spring loaded excesspressure valve 45 controls a port in the cylinder wall for relieving thecylinder pressure when it reaches a predetermined value. Accordingly,the piston I2 is not only provided with buffer means for the openingstroke, but is prevented from rebounding due to excessive buffer action.1 v In certain cases, it is desirable to reclose the breaker as soon as'possible after it has been opened to clear a fault condition. For suchoperation, it is necessary that the piston I2 be permitted springs 4Idownward to closed circuit position immediately after the openingoperation without appreciable retarding effect. For this purpose anon-return 'valve indicated at 46 controls a port in the upper cylinderwall for opening under atmospheric pressure when the piston descends soas to prevent creation of a partial vacuum in the upper cylinder spacewith resultant retarding effect on` the piston. This valve of courseremains closed when the piston is moving up- Ward.

Let it now be assumed that the breaker is closed as illustrated and thatan opening operationhas been initiated by the opening of a suitablecontrol valve (not shown) for admitting gas under pressure into theinterrupting chamber by way of the supply conduit 26. As `the gas rushesside of the pistoniI2, which ear movement on upward through the chamber,it is throttled at the constriction 20 so that it flows at high velocitypast this point and enters the lower` part of the cylinder I3 to actdirectly on the contact piston I2. It will be noted that as the pistonl2 is raised to separate the contacts I and 2, the gas blast is alreadypassing through the nozzle portion 20 so that immediately upon formation of the arc it is acted upon by an intensive cooling andinterrupting blast at the nozzle. This extinguishing action is generallysufficient to interrupt the arc at a current zero before it has beendrawn to the maximum length determined by the piston stroke in thechamber I1.

The Contact arrangement with relation to the interrupting chamber andblast pressure also aids current interruption, That is, the movablecontact moves away from the nozzle restriction in the direction of theblast to draw the arc into the pressure exhaust chamber Where, from itsincaption, it is effectively surrounded for cooling and positionedaxially by an insulating hose-like blast of pressure gas. straight andat the end of the stroke has a predetermined length as compared with alooped or bowed arc.

However, the interruption of the arc at a current zero by the intensegas blast at the interrupting nozzle does not necessarily complete thecircuit opening operation since, as previously The arc is thereforedrawn pointed out, the returning recovery voltage across the breakerterminals may break down the air gap between the contacts I and 2 and socause restriking of the arc. In order to prevent this, the interruptingchamber I1 at the exhaust side of the interrupting nozzle 20 is sovented that the gas in this part of the chamber is partially entrappedto set up an effective back pressure level sucient appreciably toincrease the dielectric strength of the gas during the separation of thecontacts. It will therefore be noted that it is necessary to initiateand establish a back pressure in the exhaust chamber beyond the nozzlethroat to cause separation of the contacts, so that the arc, from itsinception, is encompassed by gas appreciably above atmospheric pressure.In the specific arrangement described, the initial or source blastlpressure is approximately 350A lbs. per sq. in. and the averagecontrolled back pressure is calculated for approximately 120# sq. in. atwhich the dielectric strength of the air may be several times the valueit would be with free venting. Using 350# blast pressure it will beappreciated that even a back pressure as high as 180 lbs. per sq. in. atthe exhaust end of the interrupting nozzle 20 has no retarding effect onthe interrupting blast velocity since'the back pressure at an orice canbe approximately 53% sure without causing decrease of the rate ofdischarge through the orifice. Also, such control of the back pressureavoids wider and disruptive stress differentials within the deviceduring high current interruptions.

The blast exhaust opening is formed by an annular valve-like controlmember 41 guided in sleeve-like manner for limited vertical, rectilinthecylinder I3. The member is biased toward its normal lower position bysprings 48 mounted on the through bolts 38 between the cylinderinterconnecting ange 31" and offset flanges or legs on the controlmember 41. The member 41 is held in spaced relation to the supportingplate 21 by nxed lock nuts 49 on the through bolts 38 so as to form anof the source presannular venting opening, the cross-sectional area ofwhich is determined by the spacing A and the circumference 0f the member41. The lock nuts 49 also provide means for adjusting the position ofthe member 41 for regulating to a fine degree the venting area.

In the specific interrupter herein described, this pre-set venting areais related both to the opening and closing operations. It is smallenough to throttle the interrupting blast so that the arc is drawn andextinguished (usually at an early current Zero) in a region of highpressure air or gas; at the same time being large enough to permitdecisive reclosure of the piston contact, under the bias of its returnsprings, immediately following the blast cut-off. In the presentinstance optimum results were attained with an initial vent area of 2.79sq. in. for an interrupting chamber cross-sectional area of 6.75 sq.in., a cross-sectional nozzle area of 1.75 sq. in. and nozzle exhaustand source pressures of lbs. per sq. in. and 350 lbs. per sq. inrespectively The ratio of the vent or exhaust area to the nozzle area istherefore approximately 1.6. When the back pressure is restricted'within the proper zone, which may vary in accordance with the characterof the extinguishing gas employed, the breaker is capable ofsuccessfully interrupting and clearing the circuit at much highervoltages than previously possible.

For example, from tests made on comparable experimental singleinterrupting units the following comparisons were observed. The nozzleemploying the restricted exhaust is capable of interrupting at least 21%more current at 44 kv. and 124% more current at 66 kv. than anequivalent nozzle exhausting to the open air, At 88 kv. the nozzleexhausting to the open air was incapable of interrupting any current atall, While.

the restricted exhaust nozzle interrupted 2280 amperes successfully.This, together with other test data, has permitted the successfulmanufacture, for commercial use, of the 138 kv. circuit breaker hereindescribed which is rated at 1,500,000 kva. interruptingy capacity.

'Ihe venting control arrangement is also provided withl means forincreasing the venting area in case unusual and abnormally highpressures, such as in excess of lbs. per sq. in., are generated withinthe interrupting chamber, for, as previously described, the member 41can move upwardly on'the guide bolts 38 against the bias of springs 48,although in usual operation the springs 48 maintain the venting areasubstantially, xed and uniform. Hence, the use of a biased valve is notessential to practice my invention, for fixed vent openings may be usedt0 effect the proper blast and exhaust pressure relationship after thelatter has been ascertained for a given breaker.

The hot exhaust gases that flow into the housing 36 are nally vented toatmosphere, after passing through ports 31', at the muffler 50 which isprovided with suitable cooling plates or the like 5I for preventing orminimizing flame emission from the breaker.

It is within the scope of my invention to employ other methods than thatspecifically described for providing a suitable pressure level in theexhaust chamber where the arc is interrupted. For example, two differentpressures may be admitted substantially simultaneously to the chambersat opposite sides of the nozzle or the exhaust chamber in such anarrangement might be connected to the main pressure source through areducing valve. l

The circuit breaker herein described automatically recloses after acomplete opening operation, i. e., as defined by closing of the mainblast control valve. It is therefore necessary that other means inseries with the breaker be provided for disconnecting the breaker withrespect to the power circuit after circuit interrup" tion and prior toreclosing of the breaker. Figs. 2 and 3 show one phase of a triple-poleoutdoor type circuit breaker of the character herein described, eachinterrupting unit of which corresponds to that illustrated by Fig. 1.The two units are mounted on high voltage shell-like insulating supports60 and 6| respectively, which are in turn mounted on a supporting frame63 composed of structural steel work. The frame 63 also supports independing relation therefrom a gas supply tank 64 which is adap-ted tosupply both breaker units through the conduits at 26, and a suitableoperating mechanism 65 for the disconnecting means hereinafterdescribed.

faces for coacting with a movable disconnecting switch blade 66 that ismounted for rotatable movement with respect to the terminals on aninsulating support 61 likewise mounted on the frame 63, Thedisconnecting switch blade 66 when rotated approximately 45 in clockwisedirection as viewed in Fig. 3 disconnects both is in connecting positionbridging the terminals 3, and the breaker units are closed, the powerand its upper terminal 4.

Any suitable means may be provided for operating the blade 66, and byway of example an operating rod 68 secured to the blade and ticing thisinvention One such arrangement is described and claimed in a copendingapplication Serial No. 367,789, iiled November 29, 1940, by Carl Thumimand Alexander C. Boisseau for Circuit breaker operating system.

It should be understood that my invention is not limited to specificdetails of construction and arrangement thereof herein illustrated, andthat changes and modifications may occur to one skilled in the artwithout departing from the What I claim as new and desire t secure byLetters Patent of the United States is:

1. A high voltage electric circuit breaker of the gas blast typecomprising relatively movable contacts, an elongated are extinguishingchamber having a restricted cross-sectional area at which said contactsare separable to form an arc gap, a source of gas pressure for supplyingto said chamber at one side of said restriction an arc extinguishing gasunder pressure so that the arc in said restriction is blast,

for further increasmg the cross-sectional area of/said exhaust openingwhen the pressure in said extinguishing mined amount.

4. high voltage gas blast circuit breaker striction, said fixed contactbeing disposed in said chamber at the pressure entrance end thereof andsaid movable contact being disposed at the exhaust end of said chamber,and a piston connected to said movable contact and operable by gaspressure for drawing the power arc at said movable Contact axially intosaid exhaust chamber in the direction of the gas blast so that said arcis enveloped by said gas blast.

5. A high voltage gas blast circuit breaker comprising an insulatinginterrupting chamber, contacts separable to form an arc gap in saidchamber, said chamber having a constriction through which a gas underpressure is directed to extinguish arcing at said gap, said chamber atthe exhaust side of said constriction being of sufficient sizesubstantially to enclose said arc gap, and means for so restraining flowof blast gas from said exhaust chamber that a pressure level is built upin said exhaust chamber sufiicient to increase appreciably thedielectric strength of said gas by the time said contacts separate forpreventing restriking of the arc after interruption at a. current zero,said pressure level being related to the gas pressure at the entranceside of said constriction so that the effectiveness of the interruptinggas blast through said constriction is not impaired.

6. A high voltage electric circuit breaker of the gas blast typecomprising relativel1 xed and movable rod contacts disposed in verticalaligni ment, a tubular sleeve-like arc extinguishing chamber in whichsaid contacts are separable to form an arc gap, the point of contactseparation being at a restricted section of said chamber, a source ofgas pressure for supplying an arc extinguishing gas to said chamber, asubstantially circular port defining a radial exhaust opening at theupper end of said chamber of such predetermined cross-sectional areawith respect to the cross-sectional area of said restricted section thatthe gas pressure within said chamber is maintained sufficiently highduring the gas blast to prevent breakdown of said gap after arcinterruption, spring-biased means for further increasing thecross-sectional area of said exhaust opening in accordance Iwithpredetermined increase of pressure Within said chamber, and a pistondisposed at the upper part of said chamber connected to the movablecontact for causing separation of said contacts in response to theadmission of gas under pressure to said chamber, said piston and movablecontact being mounted for reciprocal movement concentrically with repectto said radial exhaust opening.

7. A high voltage electric circuit breaker of the gas blast typecomprising relatively fixed and movable rod contacts disposed invertical alignment, an insulating tube forming a sleeve-like arcextinguishing chamber in which said contacts are separable,1 the pointof contact separation being at a restricted section of said chamber soas to form the initial arc gap in said section, a source of gas pressurefor supplying an arc extinguishing gas to the lower part of saidchamber, a substantially annular member deiining an exhaust opening atthe upper end of said chamber, said opening having a minimumpredetermined cross-sectional area with respect to the cross-sectionalarea of said restricted section so arranged that the gas pressure withinsaid chamber is maintained sufciently high during the gas blast t0prevent breakdown of said gap after arc interruption, spring meanscoacting with said annular member opposing the chamber `gas pressure forpermitting further increase in the cross-sectional area of said exhaustopening in accordance with predetermined increase of pressure withinsaid chamber, and a. piston disposed at the upper part of said chamberconnected to the movable contact for causing separation of said contactsin response to the admission of gas under pressure to said chamber, saidpiston and movable contact being mounted for reciprocal movement withinsaid springbiased member.

8. A high voltage electric circuit breaker of the gas blast typecomprising relatively fixed and movable rod contacts disposed invertical alignment, an insulating tube forming a sleeve-like arcextinguishing chamber in which said contacts are separable to form anarc gap, the point of contact separation being at a restricted sectionof said chamber, a high voltage insulating shell surrounding said tube,a source of gas pressure for supplying an arc extinguishing gas to thelower end of said tube, a member normally spaced with respect to saidtube dening therewith an exhaust opening at the upper end of saidchamber having a predetermined minimum cross-sectional area, said areabeing about 1.6 times the cross-sectional area of said restrictedsection whereby the gas pressure within said chamber is maintainedsufliciently high during the gas blast to prevent breakdown of said gapafter arc interruption, means resiliently biasing said member towardsaid predetermined minimum spacing so that the cross-sectional area ofsaid exhaust opening can be further increased in accordance withpredetermined increase of pressure within said chamber, a pistondisposed at the upper part of said chamber connected to the movablecontact for causing separation of said contacts in response to theadmission of gas under pressure to said chamber, a cylinder for saidpiston having valve controlled means for regulating the speed of saidpiston in both directions, a housing for said cylinder and membermounted at the upper end of said insulating shell arranged to receivethe arc chamber exhaust gases, and cooling structure in said housingthrough which said gases are directed to atmosphere.

WILLIAM K. RANKIN.

